The present invention relates to a method for mounting an electronic component by means of arranging and sealing of the electronic component on an object such as a circuit board to which the component is mounted and, an apparatus and a dispenser used in the method.
A technique called as COB (CHIP ON BOARD) has attracted attention in recent years, as a way of mounting electronic components on a circuit board, in which electronic components are mounted onto electrodes on a circuit board in a state of the electronic components faced downward. The COB technique will be described with reference to the drawings.
FIG. 10A is a flow chart of the conventional COB method. Based on this figure, the description is made. Referring first to FIG. 10B, according to the conventional COB method, an electronic component b is first arranged and bonded to a circuit board d. Electrode parts c as shown in FIG. 10B are provided on the circuit board d for the electric connection to the electronic component b. The circuit board d is held at a stage a in FIG. 10B. Meanwhile, electrode parts of the electronic component b have bumps e to be bonded with the electrode parts c of the circuit board d. Each bump e is coated with a silver paste or the like for the bonding. The electronic component b is transferred while being sucked by a nozzle f, and positioned at an arrangement position on the board d. After the electronic component b is arranged on the board d, the silver paste is fused by heat thereby to bond the electronic component. Thereafter, a sealant is applied in the periphery of the electronic component b as indicated in FIG. 10C. The sealant i is applied by a dispenser h along a higher position side of the electronic component b after the circuit board d is held slantwise with the use of, for instance, an inclination stage g shown in FIG. 10C. In this manner, the applied sealant i is allowed to flow to a lower portion of the electronic component b along the inclination of the circuit board d. The sealant i is set with heat to complete the bonding. Reference symbol j in FIG. 10C indicates a positioning base for positioning the circuit board d.
The conventional method as above finds difficulty in flowing sealant i to the lower portion of the electronic component b, because a gap between a lower face of the electronic component b and the circuit board d is as narrow as several tens xcexcm, and moreover the sealant i is highly viscous. A feed time for the flow of sealant i is consequently apt to be lengthy, in other words, production time is lengthened thereby lowering production efficiency. Besides, the sealant i fed to the gap tends to be insufficient in feed amount, resulting in the formation of air bubbles which are to be enclosed. When the air bubbles are present between the component b and the circuit board d, and the periphery of the electronic component b is sealed to tightly close the gap between them, an expansion/shrinkage of the air in the bubbles will occur due to change of the surrounding temperature. A pressure increase or decrease due to the expansion/shrinkage of air bubbles sometimes invites breaks of the electronic component b or the humidity in the air bubbles causes corrosion of the electrode or the like, thus leading to mounting faults.
The present invention is devised to solve the aforementioned issues, and has for its object to provide a method for mounting an electronic component by applying a sealant beforehand at an arrangement position of the component on an object where the electronic component is to be mounted thereby to positively apply the sealant under the electronic component, so that the electronic component can be sealed quickly and sufficiently with the occurence of breaks, corrosion or the like mounting failures being reduced, thereby improving production efficiency, and an apparatus and a dispenser used in the method.
In order to accomplish the above-described objective, a method for mounting an electronic component according to a first aspect of the present invention comprises:
a first application process of applying a sealant to a position of an object to which an electronic component is to be mounted where the electronic component is to be arranged, in a manner to avoid an electrode part of the object;
a bond process of arranging and bonding the electronic component at the arrangement position; and
a second application process of applying a sealant at least partly to periphery of the electronic component after bonded onto the object.
According to a second aspect of the present invention, in the first aspect, at least the first application process among the first and second application processes uses a writing method.
According to a third aspect of the present invention, in the first aspect, the first application process uses a screen print method.
According to a fourth aspect of the present invention, in any one of the first-third aspects, different sealants are used in the first and second application processes.
According to a fifth aspect of the present invention, in the fourth aspect, the sealant in the first application process has heat cycle function and moisture resistance and resists being mingled with air bubbles, while the sealant in the second application process smoothly fits to a bump of an electrode part of the electronic component, and has good fluidity and low surface tension.
According to a sixth aspect of the present invention, in any one of the first-fifth aspects, the sealant in the first application process is multifunctional epoxy, while the sealant in the second application process is one selected from silicone, flame retardant epoxy and acrylic resin.
According to a seventh aspect of the present invention, an apparatus for mounting an electronic component is provided, which comprises:
a holding device for holding an object to which the electronic component is to be mounted;
a first applying device for applying a sealant to an arrangement position of the object held by the holding device where the electronic component is to be arranged, in a manner to avoid an electrode part of the object;
a bonding device for arranging and bonding the electronic component at the arrangement position of the object; and
a second applying device for applying a sealant at least partly to periphery of the electronic component after bonded on the object.
According to an eighth aspect of the present invention, in the seventh aspect, at least the first applying device among the first and second applying devices is a writing device.
According to a ninth aspect of the present invention, in the seventh aspect, the first applying device is a screen printing device.
According to a 10th aspect of the present invention, in any one of the seventh-ninth aspects, different sealants are used in the first and second applying devices.
According to an 11th aspect of the present invention, in the 10th aspect, the sealant used by the first applying device has heat cycle function and moisture resistance and resists being mingled with air bubbles, while the sealant used by the second applying device smoothly fits to a bump of an electrode part of the electronic component, and has good fluidity and low surface tension.
According to a 12th aspect of the present invention, in any one of the seventh-11th aspects, multifunctional epoxy is used as the sealant used by the first applying device, while one selected from silicone, flame retardant epoxy, and acrylic resin is used as the sealant used by the second applying device.
According to a 13th aspect of the present invention, in any one of the seventh-12th aspects, the first applying device has a dispenser equipped with a plurality of discharge openings for the sealant, and control devices for controlling discharge amounts of the sealant from the corresponding discharge openings individually.
A dispenser according to a 14th aspect of the present invention is used in the mounting apparatus in any one of the seventh-13th aspects, which has a plurality of discharge openings, wherein sealant feed paths are provided individually to the corresponding discharge openings.
According to a 15th aspect of the present invention, in any one of the first-sixth aspects, a thickness of the sealant applied in the first application process is not smaller than a height of the electrode of the electronic component and a height of the electrode of the object.
According to a 16th aspect of the present invention, in any one of the seventh-13th aspects, a thickness of the sealant applied by the first applying device is not smaller than a height of the electrode of the electronic component and a height of the electrode of the object.
In the first aspect of the present invention, the electronic component is arranged at the position of the object to which the electronic component is to be mounted and where the sealant is applied beforehand in the first application process. The sealant is quickly, sufficiently and forcibly applied in the first application process simply by avoiding the electrode at the arrangement position, to be in tight contact with the arranged electronic component and the object, and then, without causing any obstruction to a successive bonding of electrodes of the electronic component and the object, the bonding of the electrodes is performed usually. In the second application process, the sealant is applied to the periphery of the electronic component in the same manner as conventionally, which is enough to send a sealant to the sealant applied beforehand under the electronic component. The second application process is accordingly conducted speedily and sufficiently. Air bubbles are hard to mingle with the sealant between the electronic component and the object, whereby mounting failures due to breakage or corrosion of the electronic component because of the air bubbles can be reduced. The sealant is applied each time in a short time although applied twice, so that a production time is shortened and production efficiency is improved. The first application process serves to bond the electronic component arranged thereafter to the circuit board, and therefore the electronic component is prevented from being displaced after the arrangement. Moreover, the electronic component is bonded and sealed with improved performance, whereby a yield and product quality are enhanced.
In the second and eighth aspects of the present invention, an application locus and a movement speed in the writing method can be set freely, thereby to easily cope with any arrangement of electrodes on the object. Moreover, any required application density and application amount are satisfied with ease. Particularly, the writing method utilized in the first application is effective to reduce mounting failures furthermore. Since an application position of the sealant is correctly controlled, even the sealant of low viscosity does not flow to the electrodes and thus does not hinder the bonding of electrodes once a safe gap is properly secured to the electrodes. The low viscous sealant improves working efficiency further owing to its good fluidity.
In the third and ninth aspects of the present invention, any arrangement of electrodes on the object is coped with by the print pattern set beforehand to a screen, and a required application density is ensured, whereby mounting failures are decreased furthermore. The sealant can be applied instantaneously simply by opening/closing the screen and moving a squeegee to a plurality of electronic component arrangement positions at one time. Working efficiency is improved furthermore.
The fourth-sixth and 10th-12th aspects of the present invention can cope well with different application conditions such as different application methods, different instruments, etc. between the first and second application processes. Thus, each of the first and second applications can be performed well.
According to the seventh aspect, when the first applying device moves the dispenser, e.g., in three dimensions to the object held by the holding device, the sealant can be applied to the arrangement position except the electrode. Thereafter, the electronic component is arranged to the arrangement position by the bonding device. As a result, the bonding operation can be performed while the electrodes of the electronic component and the object confront each other without being disturbed by the sealant. Then, by the second applying device, the dispenser is moved and the sealant is applied to the periphery of the bonded electronic component, so that the sealing is completed. The mount method is hence carried out automatically.
According to the 13th aspect of the present invention, since the feed amounts of the sealant to the plurality of discharge openings are controlled individually, the application amount of the highly viscous sealant by the whole of the dispenser can be finely and correctly controlled to fit to a variety of application conditions in an optimum manner. If the discharge amount of the sealant from each discharge opening is controlled with a position of the discharge opening taken into consideration, the application amount can be effectively controlled, for instance, so that when the application locus is curved, the application amount is small at an inner side of a curved application locus and large at an outer side of the application locus, that is, to be uniform as a whole.